Oxidative leaching process with cupric ion in hydrochloric acid media for recovery of Pd and Rh from spent catalytic converters

Abstract

h i g h l i g h t s• A new leaching process based on Cu 2+ /HCl media for recovering Pd and Rh from spent autocatalytic converters is presented.• Palladium and rhodium were efficiently leached, with attained maximum yields of 95% and 86%, respectively.• Temperature, time, and HCl and Cu t r a c tThe recycling of platinum-group metals from wastes such as autocatalytic converters is getting growing attention due to the scarcity of these precious metals and the market pressure originated by increase of demand in current and emerging applications. Hydrometallurgical treatment of such wastes is an alternative way to the most usual pyrometallurgical processes based on smelter operations. This paper focuses on the development of a leaching process using cupric chloride as oxidising agent, in HCl media, for recovery of palladium and rhodium from a spent catalyst. The chloride media allows the adequate conditions for oxidising and solubilising the metals, as demonstrated by equilibrium calculations based on thermodynamic data. The experimental study of the leaching process revealed that Pd solubilisation is clearly easier than that of Rh. The factors temperature, time, and HCl and Cu 2+ concentrations were significant regarding Pd and Rh leaching, the latter requiring higher factor values to achieve the same results. Leaching yields of 95% Pd and 86% Rh were achieved under optimised conditions (T = 80• C, t = 4 h, [HCl] = 6 M, [Cu 2+ ] = 0.3 M).

Recovery and Then Individual Separation of Platinum, Palladium, and Rhodium from Spent Car Catalytic Converters Using Hydrometallurgical Technique followed by Successive Precipitation Methods

“…e use of aqua regia and other HCl/HNO 3 mixtures produces nitrous vapors emission, due to several intermediate and final species generation such as NOCl, NO, NO 2 , and HNO 2 , besides Cl 2 generation, as mentioned elsewhere. e use of cupric ions leaves behind copper compounds in the leaching liquor which are themselves considered as contaminants hardly separated from leached PGMs [12,14]. erefore, these facts lead us to think about the use of efficient and ecofriendly leaching processes.…”

Dissolution of Metal Supported Spent Auto Catalysts in Acids

“…Platinum did not occur in solution after leaching, or its content in liquid phase was low in trace level, which was in line with expectations. Dissolution of PGMs is only possible and performed with strong oxidants: in widely known mixtures of HCl/HNO 3 , in alternative chloride precursors such as AlCl 3 , alone or mixed with HCl, using HNO 3 as oxidant or in other common leachant mixture like HCl/H 2 O 2 or HCl/Cl 2 [9][10][11].…”

Palladium(II) and N,N′-dimethyl-N,N′-dicyclohexylthiodiglycolamide – The extracted species from concentrated chloride solutions

“…In hydrometallurgy, the most common leaching media for PGMs is aqueous hydrochloric acid, since it readily promotes the dissolution of PGMs, either alone or in the presence of additional oxidants [5]. In sequence, platinum, palladium, and rhodium need to be separated or concentrated from the chloride aqueous media.…”

“…Accordingly, the development of alternative leaching conditions (to minimize the dissolution of problematic contaminants) [5] and the adjustment of novel and / or modified solvent extraction (SX) schemes to this "new" reality [6][7][8] are subjects of wide research nowadays.…”